The present invention relates to attachments for and methods of cultivating soil by agricultural machines.
It is known to provide an agricultural machine (e.g. a tractor) with an attachment which includes a frame having a coupling device for connecting the frame to the tractor. The attachment may include at least two different soil-treating arrangements mounted on the frame one after the other. The attachment further may include wheels located on the frame, for example, between the soil-treating arrangements. The wheels may be adjustable vertically relative to the frame.
A first (i.e. the one closest to the tractor) soil-treating arrangement may constitute a set of tires, whereas a second soil-treating arrangement, which follows the first arrangement, may constitute a set of rollers and disk harrows. The wheels serve on the one hand to support the frame when a tractor, which is provided with the attachment, moves on a road. On the other hand, the wheels are used to support the frame on the ground whenever it is necessary to lift the leading end of the frame, for example in order to adjust the position (e.g. extension) of the working elements (i.e. tires) of the first soil-treating arrangement, to thereby, for example, vary the depth of cutting of the working elements into the soil.
Thus, when the tractor with the attachment reaches the end of the field to be cultivated and has now to make a turn in order to cultivate the next row, the wheels are used in order to support the entire frame in such a position relative to the soil to be treated, that the first and the second soil-treating arrangements do not engage the ground. However, the wheels leave traces on the soil, which have to be eliminated later. Moreover, the wheels may mire (i.e. sink) in the soil so that any manipulations with the attachment become considerably more complicated if possible at all. Needless to say, that the additional steps of eliminating the wheel traces on the soil considerably increase overall soil-treating expenses. It is also disadvantageous that each time the tractor makes a turn an operator has to actuate an operating lever in order to bring the wheels into engagement with the ground. The attachment is usually connected to the tractor by a three-point suspension system.
It has also been recognized that the known agricultural attachments are not satisfactory with respect to the requirements made to quality of the soil cultivated by these attachments. Shaking or crushing (breaking) elements in combination with rollers (e.g. crumbling rollers) treat the soil only on the upper surface thereof. These arrangements cannot cultivate the soil on a sufficient (i.e. adequate) depth thereof. The same is true when instead of the shaking or crushing elements one uses ground mills.
Another shortcoming resides in the fact that, since the arrangements are positively actuated, the tractor (provided with such an arrachment) has to move with a relatively small speed, otherwise the soil will be cultivated badly or different parts of the attachment may be excessively overloaded.
The attachment includes a great number of separate movable parts which are expensive on the one hand and constitute a danger of abrasion (i.e. wear) and incidents, on the other hand. On the whole, the known agricultural attachments are not economical at all.
The disk harrows are inclined relative to a direction of movement of the tractor during the cultivation. However, such harrows may comminute (i.e. mash) relatively large particles of the soil only to a certain extent (i.e. only to a certain size). Moreover, these harrows do not have the adequate cultivating effectiveness even at a relatively small depth of the soil to be cultivated. Therefore, in order to adequately cultivate the soil all the way over an adequate predetermined depth, these harrows have to be pulled a few times along one and the same field all over again.
A conventional agricultural attachment including one set of tines and rollers and another following set of tines and rollers may be more or less effectively used when the field to be cultivated has a comparatively even (i.e. non-rough) upper surface. However, should the upper surface of a field be comparatively rough (i.e. non-even), then the conventional agricultural attachment becomes even less productive since the latter cannot cultivate such a rough soil uniformly over a predetermined depth. This occurs since the rollers are effective only on the upper surface and cannot penetrate deeper in the soil to the adequate depth. As a result, a lower portion of the soil, i.e. below roots of plants in the soil cultivated by such an attachment, stiffens (i.e. hardens) which leads to developing of an excessive ground humidity in the upper portion of the soil. Obviously, any excessive ground humidity is undesirable, since it negatively affects the plants and may ruin the latter.